Thanks to all that responded. Based on received information, I am drawing the conclusion that it would be difficult to maintain a class 2b tolerance on an .090 thick FR4 epoxy board. One response indicated that this tolerance/class would be OK on metal but not FR4 epoxy since the epoxy would not retain the pitch and definition needed especially if being verified with a class 2b check gage. Any comments? Ed Cosper -----Original Message----- From: Kathy Stillings <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Date: Tuesday, June 15, 1999 2:47 PM Subject: Re: [TN] Fab: Tap and die callouts >#10-32 UNF-2B thru means National fine series thread as said and the 10-32 is >the diameter and thread count per inch. The Class 2B is the allowances and >tolerances for obtaining the fit. This is a very detailed process of pitch >diameter, major and minor diameter, root radius, etc... All in all summed up >Class 2 specifications do vary from a fit with no play when the pitch diameters >of mating parts are common to a fit with some play. Class 2 is the Cadillac of >commercial screws. If you need more detailed information like how to inspect >for class 2 please EMail me. > >################################################################ >TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >################################################################ >To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: >To subscribe: SUBSCRIBE TechNet <your full name> >To unsubscribe: SIGNOFF TechNet >################################################################ >Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. >For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 >################################################################ > > ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################